1. Field of the Invention
The invention relates to an electrical leakage detector for an output in a high voltage inverter device such as a switching regulator, an inverter or the like used in a high voltage power supply unit, a power supply unit for discharge or the like, and a high voltage inverter device including the electrical leakage detector.
2. Description of the Related Art
To supply a high voltage to various devices such as a discharge tube for a large-size plasma display, a plasma generator and the like, a high voltage inverter device such as a switching regulator or the like is used.
Generally, an inverter device with an output power value of about several W is often used, while a high voltage inverter device having an alternating-current output with an output voltage of over ten KV and a power value of several tens W or higher is used for the plasma generator or the like.
Such a high voltage inverter device having an alternating-current output of over ten KV is apt to discharge because the output is alternating-current at a high voltage and the discharge to the surrounding of the output line is dielectric discharge. Therefore, it is necessary to install the high voltage inverter device in an environment where it hardly discharges, but the output current needs to return through one path when returning to a frame ground such as a casing of the inverter or the like passing through a load.
Leakage (electrical leakage) of a high voltage along a power feeding path to the load due to an abnormal discharge or the like not only decreases the power supplied to the load but also possibly causes a serious problem on a human body due to electrical shock or causes ignition to lead to a fire. Therefore, it is necessary to constantly monitor the output voltage or current of the inverter to detect abnormality such as electrical leakage or the like and stop the operation of the inverter to thereby avoid danger.
Conventionally, in an inverter for lighting a discharge lamp, the voltage at an output end is detected and compared to the voltage at normal time to detect occurrence of abnormal discharge or the like. For example, as described in JP 2008-186615 A, the voltage on the output side of an inverter is divided by a resistor and the divided voltage is rectified and smoothed to detect the peak value or the effective value of the output voltage of the inverter. This value is compared to the normal value to monitor the presence or absence of abnormal discharge so that when abnormal discharge is detected, the operation of the inverter is stopped.